If called to action, the giant tanker would be able to drop 20,000 gallons of EPA-approved oil dispersant in one or more passes that would cover a path in the Gulf more than 300 miles long and 200 feet wide. At a rate of 5 gallons per acre, that is an area of 7,272 acres.

The jumbo jet would fly at a speed of 170 to 180 mph at an altitude of 250 feet while dropping its load. Flying to and from the drop zone, it would be able to maintain a cruise speed of 600 mph.

This is a shift in mission for the 747-200 commercial airliner, originally converted by Evergreen Aviation at a cost of $55 million to develop, manufacture and test the spraying equipment, to fight wildfires on land. With a 20,000 gallon payload, the Evergreen Supertanker is the largest firefighting aircraft in the world. It was certified for firefighting service in 2009.

With its ability to disperse a variety of liquids, foam and gels, the aircraft can conduct several missions besides firefighting, including oil spill containment, weather modification and biochemical decontamination. It disperses its payload from pressurized tanks in the aircraft’s fuselage through four independently regulated nozzles under its belly.

Because the aircraft takes off below its maximum landing weight, even when it has a full payload, there is no danger that the crew will have to dump the entire load before landing in the event of an emergency or mission cancellation.

No reconfiguration is required to switch from firefighting to oil spill control, says Jim Baynes, Evergreen’s project manager for the Supertanker. “You just change the nozzle settings,” he told TechNewsDaily. “We could be up and running in a day.” The dispersant, he said, has the consistency of diesel fuel.

Anticipating a call for its help in curtailing the destruction in the Gulf and on the shoreline, the company at its own expense relocated the Supertanker from its home base in McMinnville, Ore., to Texas for testing to ensure that it met American Society for Testing & Materials (ASTM) standards for oil spill containment. When the testing was completed in May, the aircraft was flown to Gulfport to be close to the spreading oil slick. “The aircraft is right in the heart of where everything is happening,” said Baynes.

Evergreen is no stranger to disaster relief in the Gulf area; during Hurricanes Katrina and Rita the company deployed more than 20 of its helicopters to support emergency operations. It has been involved in aerial firefighting for more than 70 years.

Evergreen is still waiting for the call from BP. “They haven’t hired us,” said Baynes.

A spokesman in BP’s America Press Office said he was not aware of any discussion on the possible use of the Supertanker.